Method and apparatus for recovering sugar



June 2, 1936.

S. C. MEREDITH ET AL METHOD AND APPARATUS'FOR RECOVERING SUGAR Filed Nov. 7, 1933 4 OESSH m ml CPA-I,

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E W B THEE ATTORNEY Patented June 2, 1936 'ME'I'HOD AND APPARATUS FOR RECOVERING SUGAR Sherman Chase Meredith, San Mateo, Paul Warren Alston, Berkeley, Saratoga, and Claren Calif Edward Taber Winslow, ee White, San Francisco, assignors to' Spreckels Sugar Company,

San Francisco, Calif., a "corporation of California Application November 7. loss, No. 696,958

9-Olaims.' (01. 127-14) The invention relates to the recovery of sugar from solutions, and more particularly to improvements in the process and apparatus for recovering sugar from dilute molasses in the manufacture of beet sugar. v

It is among the objects of the invention to provide a continuous and rapid process for recovering the sugar.

Another object of the invention is to increase the amount of sugar recovered.

Another object of the invention is to decrease the amount of lime required in the process.

Still another object of the invention is to recover substantially all of the sugar in a single direct precipitation.

' A further object of the invention is to provide a comparatively simple and inexpensive apparatus for carrying out the process.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following descrip- .tion of the invention. vlit is to be understood that we do not limit ourselves to this disclosure of species of the invention, as we may adopt variant embodiments thereof within the scope of the claims.

Referring to the. drawing:

The figure of the drawing is an elevational view, largely diagrammatic, showing the apparatus preferably employed in carrying out the method of our invention. g In' terms of broad inclusion, the method embodying the invention comprises cooling a dilute solution of the sugar, initiating a flow of the fluid, feeding powdered quicklime into the fluid, proportioning the rate of feeding the lime. to the rate of MW of the.fluid so that the latter after leaving the point of entrance of the lime carries substantially the total amount of lime required to precipitate out the sugar, then agitating the mixture and reducing the uncombined lime in the solution to smaller particles, and then cooling and circulating the mixture until substantially all the sugar has combined with the lime. The

invention also embraces suitable apparatus for 'carrying-out the method.

" In greaterdetail, and referring to the drawing, the apparatus embodying the invention comprises a heat exchanger 2 for cooling a dilute solution of molasses from which the sugar is to be recovered. The fluid is preferably delivered to the coils 3 through a duct 4 by a suitable pump (not shown); it being understood that this pump may be of any known or suitable construction. Duets 8 are also connected with the tank of the heat exchanger through which a suitable cooling fluid may be circulated. The solution is preferably cooled to about 5 to degrees centigrade at this point.

In the past it has been the practice to add the lime slowly and gradually while the solution is being stirred in a tank. In an attempt to make a continuous process a plurality of such tanks have been employed through which the fluid gradually progresses. These systems are slow and involve extensive apparatus. As opposed to these methods the present invention contemplates the immediate addition of the total amount of lime required to precipitate out the sugar, and

also contemplates the addition of this total amount of lime to a fast-moving stream of the fluid. By this improved method a rapid continuous process with simplifled apparatus is.,provided.

After being cooled in the heat exchanger 2 the fluid is-conducted by a duct 1 to a liming unit in which the full percentage of lime required to precipitate out the sugar is added to the solution.

Theliming unit is preferably in vthe nature of a funnel 8 arranged with the horizontal feeder duct 1 opening into a side thereof so that the fluid enters the funnel tangentially. A vertical duct 9 is connected with the discharge end of the funnel. By this arrangement the fluid is given a vortical movement which swirls around in the funnel or vortex pot 8 and terminates in a downwardly and fast-moving stream through the duct 9.

Powdered quicklime is fed into the upper end of the funnel 8 through a duct H connected with a cylinder l2. The lime is introduced into the cylinder through a suitable chute l3, and is carried forwardly by a feed screw M. The latter is 2'0- bodies means for varying the speed of rotation of the screw so that the rate at which the lime is fed to the duct ll may be varied.

The speed of the feed screw I4 is determined by the amount of fluid passing, through the funnel 8, and is adjusted so that the proportioning between the rate of feeding the lime and the rate of flow of the fluid is such .that the fluid leaving the funnel carries the full percentage of lime required to precipitate out the sugar.

The lime fed into the funnel is preferably directed into the throat of the vortex, where it is immediately entrained by the fluid, and carried downwardly'with the stream flowing through the" together with the suction characteristic of the fluid movement, provides an ideal condition for the reception and entrainment of the lime. If desired, the lime may be added by simply feeding it into a pipe carrying the solution, The funnel or vortex pot arrangement shown is preferred however, becauseof the efllcient manner in which the ,vortical flow entrains the lime.

Means are also provided for agitating the mixture and reducing the particles of uncombined lime to smaller size promptly after the lime has been entrained by the fluid. This -is accomplished by directing the stream of fluid in the duct 9 into a suitable mixing and grinding unit I i, such as a gear pump or colloid mill. A pump unit is preferably employed because it forces the liquid ahead as well as providing the mixing and grinding action. The prime purpose of the unit I7. is to break up the particles of tree or uncomiiined' lime and thoroughly distribute the latter throughout the mixture to promote the reaction between the limeand sugar in the solution.

Alter leaving theunit I! the fluid is delivered to a second heat exchanger l8 through a duct i9. Circulation of a cooling fluid is maintained about the coils 2i of the heatexchanger through suitable ducts 22. This cooling unit is preferably of the direct flow type, as shown, so as to allow a minimum of general mixing of the fluid and provide a. sufliciently rapid flow to keep the precipitate in suspension. From the cooling unit Iii the fluid is preferably delivered into a tank 23 through a duct 24. An impeller 26 rotated by a suitable drive 21 is provided in the tank for stirring the fluid. Suitable cooling coils 28 are also preferably provided in the tank for absorbing the heat of reaction.

If desired, the storage tank 23 may be omitted and the fluid merely circulated through suitable pipes until the reaction is completed. The provision of a tank is preferred however, since it guards against the passage of any incompletely .reacted material to the filter, insures that the tion; the additional step of hot precipitation ordinarily employed in refining processes being unnecessary.

As compared with the Steflfen process, which is the one most widely used, the method disclosed herein effects a recovery of betterthan five percent more sugar. -In a plant which handlesi75,000 tons of beets in a season the five percent saving "represents a saving of 1,662,500 pounds of sugar per season. In addition to effecting a greater recovery in sugar, the process-disclosed herein effects a saving of from 15 to 20 percent production, but it also reduces the cost and complexity of the apparatus.

We claim: 1 I

1. The method of recovering sugar from solution, which comprises conducting the solution in a continuously advancing stream and converting the solution into a. mixture from which sugar will precipitate by resolving the stream into a vortical flow and introducing lime into the vortex, increasing the availability of the lime in the stream by disrupting the coating of lime-sugar compound forming on the lime particles, and then filtering out the precipitated sugar while maintaining the volume and velocity of the solution and mixture from the point of supply to the filter.

2. The method of recovering sugar from solution, which comprises conducting the solution in a continuously advancing stream and converting the solution into a mixture from which sugar will precipitate by resolving the stream into a vertical flow and introducing lime into the vortex increasing theavailability of the lime in the stream by disrupting the coating of lime-sugar compound forming on the lime particles, forcing the reacting mixture at sustained velocity along a path 25 of suflicient length to permit a substantial completidn of reaction and then filtering out the precipitated sugar while maintaining the volume and velocity oi! the solution and mixture from the point of supply to the flltia.

3. Apparatus for recovering sugar from solution comprising a duct in which the solution may flow in a continuously advancing stream, means interposed in said duct for converting the solution into amixturefrom which sugar will precipitate, said means comprising a device for adding a continuous increment of lime to the stream, and means interposed at a subsequent point in said duct for breaking up the particles flowing in the stream to expose substantially all the lime to reaction.

' 4. Apparatus for recovering sugar from solution comprising a duct in which the solution may fiow in a continuously advancing stream, means interposed in said duct for converting the solution into a mixture from which sugar will precipitate, said means comprising a device for adding a continuous increment of lime to the stream, means interposed at asubsequent point in said duct for breaking up the particles flowing in thestream to expose substantially all the lime to reaction, and a filter into which the solution from the duct discharges.

5. Apparatus for recovering sugar from solu- 5 tion comprising a duct in which the solution may flow in a continuously advancing stream, means interposed in said duct for converting the solution into a. mixture from which sugar wfll precipitate, said means comprising a device for 6 adding a continuous increment of lime to the stream, means interposed at a subsequent point in said duct folbreaking up the particles flowing in the stream to expose substantially all the lime to reaction, and 'a filter into which the solu- 65 tion from the duct discharges, the portion or the duct between the means for breaking up the particles and the filter being or sufiicient' length to permit substantially complete reaction.

6. The method of recovering sugar from solu- 70 tion, which comprises the steps of conducting the solution .in 'a continuously advancing, stream along a path leading from a supply of the solution toa filter, adding lime to the stream at a point along said path, and disrupting the lime 75 particles in the stream at a subsequent point along said path.

7. The method of recovering sugar from solution, which comprises the steps of conducting the solution in a continuously advancing stream along a path leading from a supply oi the solution to a filter, resolving the stream at a point along said path intoa vortical flow and introducing lime into'the vortex, and disrupting the lime particles in the stream at a subsequent point along said path.

8. Apparatus for recovering sugar from solution comprising a filter, a liming unit for adding lime to the solution, means for conducting the solution from the liming unit directly to the filter, and means interposed between the liming unit and filter for breaking up the lime particles in the solution.

9. Apparatus for recovering sugar from solution comprising a filter, a liming unit including means for initiating a vortical flow 01' the solution and means for introducing lime into the vortex, means for conducting'the solution from the liming unit directly to the filter, and means interposed between the liming unit and filter for breaking up'the lime particles in the solution. SHERMAN CHASE MEREDITH.

PAUL WARREN AIBTON. f EDWARD TABER WINSLOW. CLARENCE WHITE. 

